Optoelectronic conversion header, LSI package with interface module, method of manufacturing optoelectronic conversion header, and optical interconnection system

ABSTRACT

In an optoelectronic conversion header, a ferrule holds an optical waveguide in a predetermined position so that an end face of the optical waveguide protrudes from an mounting surface of the ferrule. An electric wire is provided on the mounting surface of the ferrule, a optical semiconductor device is mounted on the mounting surface of the ferrule and electrically connected to the electric wire. From the end face of the optical waveguide, an optical signal is transferred in a transfer direction and the mounting surface of the ferrule is so arranged as to be deviated two degrees or more from a plane vertical to the transfer direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Applications No. 2004-237456, filed Aug. 17, 2004;and No. 2005-100312, filed Mar. 31, 2005, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optoelectronic conversion headerapplied to a high-speed LSI package and a manufacturing method of theoptoelectronic conversion header, an LSI package with an interfacemodule equipped with the optoelectronic conversion header, and anoptical interconnection system.

2. Description of the Related Art

Recently, a performance of large-scale integrated circuits (LSIs) issignificantly improved to achieve a high speed processing due to animproved performance of electronic devices such as bipolar transistorsand field effect transistors. However, even though the processing speedis improved in the LSI, a printed wiring board mounting the LSI is notso sufficiently improved as to have a sufficiently high signal transferrate or speed for transferring a signal from the high speed processingLSI. The transmission speed in the printed wiring board is restricteddue to following reasons. In the printed circuit board, it is necessaryto prevent a reduction in a signal quality resulting from an increase ina transmission loss, noise and electromagnetic interference in electricwires due to an increased operation frequency. The longer lines in thecircuit board need more restraint on the operation frequency to ensurethe satisfactory signal quality. In this background, it is recognized ina common sense that a system speed is limited by a packaging techniquerather than the LSI operation speed.

In view of such problems in the electrically wired systems, severaloptical devices have been proposed in which the LSI is connected viaoptical waveguides. In the optical waveguide, a signal loss has notfrequency dependency even in a range between a direct current and 100GHz or higher, and noise is not produced due to the electromagneticinterference of wiring paths and a variation in a ground potential. Theoptical waveguide can readily realize a data transmission capability ofseveral tens of Gbps. An application of the optical waveguide isproposed in Nikkei Electronics, No. 810, pp. 121-122, Dec. 3, 2001, inwhich an interface module is directly mounted on an interposer forinterconnecting the LSI to a peripheral device to transmit a high-speedsignal between the LSI and the peripheral device.

In order to realize the optical interconnection disclosed in NikkeiElectronics, No. 810, pp. 121-122, Dec. 3, 2001, the interposer isessentially provided with an optoelectronic conversion component whichconverts an optical signal into an electric signal or converts theelectric signal into the optical signal, and the optoelectronicconversion component is further required to have a small size in orderto be arranged in the interposer. This small optoelectronic conversioncomponent has a structure in which a surface emitting laser is opticallycoupled to an optical fiber, as disclosed in Jpn. Pat. Appln. KOKAIPublication No. 2000-347072. There has been proposed in connection withthis structure in Jpn. Pat. Appln. KOKAI Publication No. 2001-281503which discloses metal projections having different heights or a blockhaving an inclined plane are used to obliquely dispose an opticalsemiconductor device such as semiconductor lasers to restrain externaloptical feedback. There has been also proposed in Jpn. Pat. Appln. KOKAIPublication No. 2001-284608 in which a photodiode (PD) of rear surfaceincidence type is adhesively bonded onto a fiber having an end faceobliquely cut with respect to an optical axis.

The conventional structure disclosed in Jpn. Pat. Appln. KOKAIPublication No. 2000-347072 has a problem that if the optical fiber isinserted in a support member provided with the surface emitting laser tooptically couple the surface emitting laser to the optical fiber forassembly of the structure, the optical fiber contacts an active area ofthe optical semiconductor device and this contact easily damage theoptical semiconductor device. There is also a problem that since thesurface emitting laser is proximately disposed in parallel with theoptical fiber, the external feedback light rays are input to the surfaceemitting laser and easily generate so-called external optical feedbacknoise.

A conventional structure for suppressing the external optical feedbacknoise has been disclosed in Jpn. Pat. Appln. KOKAI Publication No.2001-281503. However, there is a problem in which a temperature changeeasily varies an inclination angle of the optical semiconductor devicein this structure that is provide with the metal projections havingdifferent heights or the block having the inclined plane to obliquelydispose the optical semiconductor device. In this structure, if thermalexpansion is caused in the metal projections or the block, variouschanges in heights of the metal projections or the block are producedand the inclination of the optical semiconductor device is changed. Inthe conventional structure disclosed in Jpn. Pat. Appln. KOKAIPublication No. 2001-281503, the external optical feedback noise is alsogenerated depending on temperature, so that the excessively largeinclination angle is set to avoid the external optical feedback noise.Another problem is the excessively low optical coupling efficiencybetween the surface emitting laser and the optical fiber resulting fromthe excessive setting of the inclination angle of the opticalsemiconductor device. Moreover, the conventional structure in Jpn. Pat.Appln. KOKAI Publication No. 2001-281503 is complicated in thestructure, and not suitable for mass production.

Furthermore, in the conventional structure disclosed in Jpn. Pat. Appln.KOKAI Publication No. 2001-281503, the entire optical semiconductordevice is inclined with respect to the member supporting the opticalfiber. The conventional structure has a gap between an end face of theoptical fiber and the optical semiconductor device, which has a distancedelivered from a multiplication of the inclination angle and a lengthbetween an optical semiconductor device end and the active area. Thus, aphoto detection area needs to be a small diameter. Especially in acombination of the high-speed photo detector, light rays exiting fromthe optical fiber are diverged to the high-speed photo detector, leadingto a problem that the optical coupling efficiency is easily decreased.The external feedback light rays does not regarded as noise between thephoto detector and the optical fiber. However, in such a case as in theinter-LSI wire lying over a relatively short distance of about 1 m atthe maximum, most of the external feedback light rays are generated dueto a reflection on the optical fiber end face on a photo detector sideor a reflection on a photo detector surface and the reflection lightrays return to a light emitter via the optical fiber so that theexternal optical feedback noise is induced. Therefore, measures forprevention of the light reflection are also needed on the photo detectorside, and the photo detector needs to be inclined in the conventionalstructure of Jpn. Pat. Appln. KOKAI Publication No. 2001-281503,resulting in the problem that the optical coupling efficiency isdecreased.

Another method to incline the optical semiconductor device is, as inJpn. Pat. Appln. KOKAI Publication No. 2001-284608, to obliquely formthe optical fiber end face together with a ferrule and adhesively bondthe optical semiconductor device to this end face. However, this methodrequires a polishing process to form the end face of the optical fiberinto the inclined surface so that it is substantially difficult tosignificantly reduce costs. In an application of the interconnectionbetween the LSI and the peripheral devices, a permissible cost is low ascompared with costs in optical communications or LANs, and there is aproblem that a time-consuming process such as the polishing processcannot be permitted.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide, at low cost andwith high performance, an optoelectronic conversion header, an LSIpackage with an interface module using the optoelectronic conversionheader, and an optical interconnection system which have simplestructure and prevent an optical semiconductor device from being damagedduring manufacture and assembly while enabling restraint of externaloptical feedback noise.

According to an aspect of the present invention, there is provided

an optoelectronic conversion header comprising:

an optical waveguide which guides an optical signal and has an end face;

a ferrule, having a mounting surface, which holds the optical waveguidein a predetermined position so that the end face of the opticalwaveguide protrudes from the mounting surface;

an electric wire provided on the mounting surface of the ferrule; and

an optoelectronic converter having an optical input/output surface,which is electrically connected to the electric wire and is mounted onthe mounting surface of the ferrule, the optical input/output surfacebeing faced to the end face of the optical waveguide so as to transferthe optical signal along a transfer direction between the opticalinput/output surface and the end face of the optical waveguide, the endface being substantially vertical to the transfer direction, and theoptical input/output surface being deviated two degrees or more from aplane vertical to the transfer direction.

According to another aspect of the present invention, there is providedan optoelectronic conversion header comprising:

an optical semiconductor device having an device surface in which asurface light emitter or a surface photo detector is formed;

an optical waveguide having an end face, which guides an optical signal,the optical signal being transferred along a transfer direction betweenthe device surface and the end face;

a ferrule having a mounting surface on which the optical semiconductordevice is mounted and a side surface crossing the mounting surface,which holds the optical waveguide so as to face the end face of theoptical waveguide to the device surface of the optical semiconductordevice at the mounting surface, the end face being substantiallyvertical to the transfer direction and the device surface being deviatedtwo degrees or more from a plane vertical to the transferred direction;and

an electric wire provided on the ferrule, extending from the sidesurface to the mounting surface and electrically connected to the devicesurface; and

a first transparent resin provided between the end face of the opticalwaveguide and the device surface of the optical semiconductor device.

According to yet another aspect of the present invention, there isprovided an LSI package to be mounted on a printed wiring boardcomprising:

an interposer equipped with a signal processing LSI and having firstelectric terminals to be electrically connected to the printed wiringboard;

an interface module including an optoelectronic conversion header and anelectrical connection terminal, which is electrically and mechanicallyconnectable to the interposer, the optoelectronic conversion headercomprising:

an optical waveguide which guides an optical signal and serves as anoptical transmission channel for the optical signal and has an end face;

a ferrule, having a mounting surface, which holds the optical waveguidein a predetermined position so that the end face of the opticalwaveguide protrudes from the mounting surface;

an electric wire provided on the mounting surface of the ferrule; and

an optoelectronic converter having a optical input/output surface, whichis electrically connected to the electric wire and is mounted on themounting surface of the ferrule, the optical input/output surface beingfaced to the end face of the optical waveguide so as to transfer theoptical signal along a transfer direction between the opticalinput/output surface and the end face of the optical waveguide, the endface being substantially vertical to the transfer direction; and theoptical input/output surface being deviated two degrees or more from aplane vertical to the transfer direction

According to furthermore aspect of the present invention, there isprovided an LSI package to be mounted on a printed wiring boardcomprising:

an interposer equipped with a signal processing LSI and havingconnecting electric terminals to be electrically connected to a printedwiring board;

an interface module including an optoelectronic conversion header and anelectrical connection terminal, which is electrically and mechanicallyconnects to the interposer, the optoelectronic conversion headercomprising:

an optical semiconductor device having an device surface in which asurface light emitter or a surface photo detector is formed;

an optical waveguide having an end face, which guides a optical signaland serves as an optical transmission channel for the optical signal,the optical signal being transferred along a transfer direction betweenthe device surface and the end face;

a ferrule having a mounting surface on which the optical semiconductordevice is mounted and a side surface crossing the mounting surface, theferrule holding the optical waveguide so as to face the end face of theoptical waveguide to the device surface of the optical semiconductordevice at the mounting surface, the end face being substantiallyvertical to the transfer direction and the device surface being deviatedtwo degrees or more from a plane vertical to the transferred direction;and

an electric wire provided on the ferrule, extending from the sidesurface to the mounting surface and electrically connected to the devicesurface; and

a first transparent resin provided between the end face of the opticalwaveguide and the device surface of the optical semiconductor device.

According to also furthermore aspect of the present invention there isprovided a method of manufacturing an optoelectronic conversion header,the method comprising:

mounting an optical semiconductor device having a rear surface and andevice surface in which a surface light emitter or a surface photodetector is formed, on an mounting surface of a ferrule, andelectrically connecting the optical semiconductor device to an electricwire on the ferrule, the ferrule having a mounting surface and ainsertion hole for holding the optical waveguide;

disposing a stopper member having a surface substantially parallel tothe rear surface of the optical semiconductor device on the rearsurface; and

inserting the optical waveguide into the insertion hole so as to face anend face of the optical waveguide to the device surface of the opticalsemiconductor device, the end face of the optical waveguide beingsubstantially vertical to a transfer direction of a optical signalguided by the optical waveguide between the end face and the devicesurface, and the device surface being inclined to a plane vertical tothe transferred direction, and putting a transparent resin between thedevice surface and the end face while the stopper member is disposed onthe rear surface of the optical semiconductor device.

According to yet furthermore aspect of the present invention, there isprovided an optical interconnection system comprising:

an optical waveguide which guides an optical signal and has first andsecond end faces optically coupled to each other;

first and second optoelectronic conversion headers optically coupled bythe optical waveguide, the first optoelectronic conversion headercomprising:

a first ferrule, having a first mounting surface, which holds theoptical waveguide in a first predetermined position so that the firstend face of the optical waveguide protrudes from the first mountingsurface;

an first electric wire provided on the first mounting surface of thefirst ferrule; and

a light emitting device having a light emitting surface, which iselectrically connected to the first electric wire and is mounted on thefirst mounting surface of the first ferrule, the light emitting surfacebeing faced to the first end face of the optical waveguide so as totransfer the optical signal along a first transfer direction from thelight emitting surface to the first end face of the optical waveguide,the first end face being substantially vertical to the transferdirection; and the light emitting surface being deviated two degrees ormore from a plane vertical to the transfer direction; and

the second optoelectronic conversion header comprising:

a second ferrule, having a second mounting surface, which holds theoptical waveguide in a second predetermined position so that the secondend face of the optical waveguide protrudes from the second mountingsurface;

an second electric wire provided on the second mounting surface of thesecond ferrule; and

a photo-detecting device having a photo-detecting surface, which iselectrically connected to the second electric wire and is mounted on thesecond mounting surface of the second ferrule, the photo-detectingsurface being faced to the second end face of the optical waveguide soas to transfer the optical signal along a second transfer direction fromthe second end face of the optical waveguide to the photodetectingsurface, the second end face being substantially vertical to thetransfer direction; and the detecting surface being deviated two degreesor more from a plane vertical to the transfer direction.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a sectional view schematically showing an LSI package with aninterface module comprising an optoelectronic conversion headeraccording to a first embodiment of the present invention;

FIG. 2 is a sectional view schematically showing the optoelectronicconversion header at a transmitting end according to the firstembodiment of the present invention;

FIG. 3 is a schematic sectional view showing a dimensional example of anoptical semiconductor device to explain how the optical semiconductordevice shown in FIG. 1 is disposed;

FIG. 4 is a sectional view schematically showing one example of how theoptical semiconductor device shown in FIG. 3 and an optical fiber as alight guide are arranged with respect to each other;

FIG. 5 is a sectional view schematically showing the optoelectronicconversion header at a receiving end according to the first embodimentof the present invention;

FIG. 6 is a sectional view schematically showing one example of how theoptical semiconductor device in the optoelectronic conversion headershown in FIG. 5 and the optical fiber as the light guide are arrangedwith respect to each other;

FIGS. 7A and 7B are a plan view and a sectional view schematicallyshowing a light emitter mounted on the optoelectronic conversion headerat the transmitting end according to a second embodiment of the presentinvention;

FIGS. 8A and 8B are a plan view and a sectional view schematicallyshowing a photo detector mounted on the optoelectronic conversion headerat the receiving end according to the second embodiment of the presentinvention;

FIGS. 9A and 9B are a plan view and a sectional view schematicallyshowing a four-channel array of the light emitters mounted on theoptoelectronic conversion header according to a modification of thesecond embodiment of the present invention;

FIG. 10 is a sectional view schematically showing the optoelectronicconversion header according to a third embodiment of the presentinvention;

FIG. 11 is a sectional view schematically showing the optical interfacemodule comprising a driver IC and the optoelectronic conversion headershown in FIG. 10;

FIG. 12 is a sectional view schematically showing the optoelectronicconversion header according to a fourth embodiment of the presentinvention;

FIG. 13 is a sectional view schematically showing the optical interfacemodule comprising a driver IC and the optoelectronic conversion headershown in FIG. 12;

FIGS. 14A, 14B and 14C are sectional views schematically showing aprocess of manufacturing the optoelectronic conversion header accordingto a fifth embodiment of the present invention;

FIG. 15 is a perspective view schematically showing a ribbon opticalfiber to explain a method of shaping an end face of the optical fiberprovided in the LSI package as a referential example;

FIGS. 16A and 16B are sectional views schematically showing a cuttingdevice according to a method of cutting the optical fiber shown in FIG.15 as a first referential example;

FIGS. 17A and 17B are sectional views schematically showing the cuttingdevice according to the method of cutting the optical fiber shown inFIG. 15 as a second referential example;

FIG. 18 is a perspective view schematically showing the ribbon opticalfiber to explain the optical fiber end face shaping method;

FIGS. 19A, 19B and 19C are sectional views schematically showing a coverremover to remove a cover from the ribbon optical fiber as shown in FIG.18, and a removing process thereof;

FIGS. 20A, 20B and 20C are sectional views schematically showing thecover remover to remove the cover from the ribbon optical fiber as shownin FIG. 18, and the removing process thereof;

FIGS. 21A and 21B are sectional views schematically showing the cuttingdevice which cuts, as shown in FIG. 18, the optical fiber from which acover resin has been removed;

FIG. 22 is a sectional view schematically showing a cut state of theoptical fiber cut in FIGS. 21A and 21B;

FIG. 23 is a sectional view schematically showing an optical fiberconnector to connect the cut optical fibers;

FIG. 24 is a sectional view showing a state in which the cut opticalfibers are connected using the optical connector shown in FIG. 23;

FIG. 25 is a sectional view schematically showing another optical fiberconnector to connect the cut optical fibers;

FIG. 26 is a sectional view schematically showing the cut state of theoptical fiber cut in FIGS. 21A and 21B; and

FIG. 27 is a sectional view showing a state in which the cut opticalfibers as shown in FIG. 26 are connected using the optical connectorshown in FIG. 25.

DETAILED DESCRIPTION OF THE INVENTION

There will be described an optoelectronic conversion header, an LSIpackage with an interface module provided with the optoelectronicconversion header, a method of manufacturing the optoelectronicconversion header, and an optical interconnection system according toembodiments of the present invention, in reference to the drawings.

FIG. 1 shows a structure of a LSI package with an interface modulecomprising the optoelectronic conversion header according to theembodiments of the present invention. This structure of the LSI packagewith the interface module is described in U.S. application Ser. No.10/778,030 filed earlier by the present inventors including Hamasaki etal. on Feb. 3, 2004. The entire contents of the U.S. application Ser.No. 10/778,030 are incorporated herein by reference. As the presentapplication is incorporated in the specification of this US Application,the LSI package with the interface module shown in FIG. 1 will be simplydescribed below. This US Application should be referred to for a betterunderstanding of the LSI package with the interface module.

In FIG. 1, solder balls 22 are provided on a lower surface of aninterposer substrate 21, and the interposer substrate 21 is fixed to aprinted wiring board (not shown) via the solder balls 22. An LSI 23 forsignal processing is placed on the interposer substrate 21 which isprovided with an electric connection terminal 24. A short lengthelectrical wiring substrate 25 is electrically and mechanicallyconnected to the electric connection terminal 24. On this wiringsubstrate 25, there are provided a driving IC 27 and an optoelectronicconversion module 28 as an optical semiconductor device driven by thedriving IC. An optical fiber 5 is mechanically connected to theoptoelectronic conversion module 28, and the optoelectronic conversionmodule 28 converts an electric signal to an optical signal to be emittedto the optical fiber 5, or the optical signal brought by the opticalfiber 5 is converted to the electric signal by the optoelectronicconversion module 28. The electric signal output from the signalprocessing LSI 23 and processed at a high speed is supplied to theinterposer substrate 21, the electric connection terminal 24, the wiringsubstrate 25 and the optoelectronic conversion module 28 through thedriving IC 27 where it is converted to the optical signal to be emittedto the optical fiber 5, while the optical signal brought by the opticalfiber 5 is converted to the electric signal by the optoelectronicconversion module 28, and then supplied to the driving IC 27 and thesignal processing LSI 23 via the wiring substrate 25, the electricconnection terminal 24 and the interposer substrate 21.

A heat sink 31 is mounted on the signal processing LSI 23 and the wiringsubstrate 25 to cool the signal processing LSI 23 and the wiringsubstrate 25, and a cooling fan 32 is provided on the heat sink 31 torelease heat from the heat sink 31.

As described above, the high-speed signal from the signal processing LSI23 is supplied not to the mounting board via the solder balls 22 but tothe driving IC 27 via the electric connection terminal 24 and the wiringsubstrate 25. The electric signal is converted to the optical signal bythe photoelectric conversion module 28, and then the optical signal isguided to the optical fiber 5. In the package shown in FIG. 1, theinterface module including the wiring substrate 25, the driving IC 27,the photoelectric conversion module 28 and the optical fiber 5 ismounted on the interposer substrate 21 equipped with the signalprocessing LSI 23. That is, the interface module can be mounted on theinterposer substrate 21 after the signal processing LSI 23 is mounted onthe interposer substrate 21. Further, the heat sink 31 and the coolingfan 32 are mounted on the interface module and the signal processing LSI23, so that the heat is released from the signal processing LSI 23 viathe heat sink 31.

The LSI package with the interface module having such a structure can bemounted on the board in accordance with totally the same procedure andconditions as those under which a current mounting device such as areflow device is used to mount the LSI on the mounting boardmanufactured in an existing production line. That is, the interposersubstrate 21 equipped with the signal processing LSI 23 is first mountedon the board together with other electronic components using an existingmethod, and then the interface module is put thereon from the above andfixed with, for example, screws or an adhesive, thereby realizing thestructure shown in FIG. 1 on the mounting board.

At that time, production can be carried out without changing theexisting mass production line up to a process of mounting the interposersubstrate 21 on the board. In a process of manufacturing the opticalinterconnection module, it is needed to install the interface module butother special operations are not required. Moreover, a process ofplacing the interface module does not require particularly highlyaccurate alignment, for example, an alignment with accuracy of ±10 μm,and accuracy for general electric connectors may be sufficient, whichdoes not lead to a notable increase in costs for the mounting process.In other words, by using the available inexpensive printed wiring boardsuch as a glass epoxy substrate and the existing mounting method, it ispossible to realize a high-speed board provided with a high-speed signaltransmission lines, which is generally difficult to realize with theelectrical printed wiring board, for example, having a transmissionspeed of 20 Gbps per wire.

The LSI package with the interface module described above is an assemblyof electrical devices or parts except for the optoelectronic conversionmodule 28 and the optical fiber 5, and a current semiconductor mountingtechnique can be applied thereto, thus allowing lower costs by massproduction. In the following explanation, an optical semiconductordevice subassembly structure to which the optoelectronic conversionmodule 28 and the optical fiber 5 are optically and mechanically coupledwill be referred to as an optoelectronic conversion header 100. If theoptical semiconductor device provided in the optoelectronic conversionmodule 28 is a light emitting type, the optoelectronic conversion header100 will be referred to as the transmitting side optoelectronicconversion header 100, and if the optical semiconductor device providedin the optoelectronic conversion module 28 is a photo detecting type,the optoelectronic conversion header 100 will be referred to as thereceiving-side optoelectronic conversion header 100.

If the cost required for this optoelectronic conversion header 100 canbe reduced, it is possible to decrease the cost for the high-speedwiring board using the optical semiconductor device, which can be asignificant contribution to higher capacity and upgrading of informationand communication equipment. The optoelectronic conversion header 100capable of reducing the costs in such an LSI package with the interfacemodule will be described below in greater detail.

There are various factors of increasing a cost in the aforementionedoptoelectronic conversion header 100, for example, a defective inassembly of the optoelectronic conversion header 100, in particular, afault in which the optical semiconductor device is mechanically damagedby an optical waveguide when the optical waveguide such as the opticalfiber is placed and fixed or a fault in characteristics that causesexternal optical feedback noise. The costs of the defective products areadded to manufacturing costs of non-defective products, resulting in anincrease in cost. It is to be noted that if the optical fiber isobliquely polished as described above, a still larger processing cost isfurther added to the manufacturing costs. Various embodiments of theoptoelectronic conversion header 100 of the present invention capable ofreducing the costs will be described below.

First Embodiment

FIG. 2 is a sectional view schematically showing an optoelectronicconversion header 100 at a transmitting side according to a firstembodiment of the present invention.

In the optoelectronic conversion header 100 at the transmitting sideshown in FIG. 2, an optical fiber 5 is held by a ferrule 1, which servesas an optical waveguide to guide an optical signal. The opticalwaveguide is not limited to the optical fiber 5, and may be an opticalwaveguide film. The optoelectronic conversion header 100 in which theoptical fiber 5 is held by the ferrule 1 will be described below. Theoptical fiber 5 is inserted into an insertion hole formed in the ferrule1, and this ferrule 1 aligns an end face of the optical fiber 5 with asurface light emitter 3 such as a vertical cavity surface emitting laser(VCSEL). Thus, the optical signal guided via a core 5A of the opticalfiber 5 is emitted from its end face to a light-emitting portion of thelight emitter 3. It is to be noted in FIG. 2 that a numeral 5B indicatesa cladding of the optical fiber 5. An optical input/output surface 3A isfaced to the end face of the optical fiber 5 so as to transfer theoptical signal along a transfer direction between the opticalinput/output surface 3A and the optical fiber 5.

Furthermore, in the ferrule 1, an electric wire 2, that is, a lineelectrodes are patterned on an end face and a side surface 1A of theferrule 1 so that the electric wire 2 is electrically connected to aterminal of the surface light emitter 3 via a mounting bump 4, and thesurface light emitter 3 is fixed to the end face of the ferrule 1 by atransparent resin 6 as an under-fill material and an adhesive.

The ferrule 1 is formed in such a manner that epoxy resin in which, forexample, glass fillers each having a size of about 30 μm are mixed atabout 80% is cast into a die, and the electric wire 2 is formed on thisferrule 1, for example, by pattern metallization utilizing a metal maskand sputtering. Such a manufacturing method allows mass production ofthe ferrule 1 with the electric wire at very low cost while the ferrule1 is provided with a very high accuracy of 1 μm or lower. The electricwire 2 is formed to extend from the end face of the ferrule 1 where thesurface light emitter 3 is placed to the side surface of the ferrule 1.

Materials that can be used for the ferrule 1 include, in addition toepoxy resin mentioned above, polyphenylene sulfide (PPS), liquid crystalpolymer (LCP), polyamide resin, silicone resin, acrylic resin, and aresin in which the glass fillers are mixed into polycarbonate resin.Various materials and connection methods can be used for the opticalsemiconductor device mounting bump 4, for example, a hot melted typesolder bump, a thermal compression bonding type Au bump or a solid statebonding type Sn/Cu bump. For the optical fiber 5, a silica-basedmultimode graded index (GI) fiber 5 is used such as an optical fiberhaving a core diameter of 50 μm, a cladding diameter of 125 μm and an NAof 0.21. It is also possible to use, for the optical fiber 5, amulti-component-glass-based optical fiber or a plastic optical fiber.

Here, the end face of the optical fiber 5 is formed to be substantiallyvertical to a light-guiding direction of the optical fiber 5, and in acase of, for example, the silica fiber, it is slightly scratched by adiamond blade and a lateral pressure is applied thereto to form astress-broken surface, a so-called cleaved surface. An exclusive cutteris commercially available to form the cleaved surface, so that anoptical fiber array, that is, a ribbon fiber can be collectively cleavedin an aligned manner. Further, in a case of, for example, the plasticfiber, an end face forming method including, for example, verticalcutting with a knife or a hot plate molding may be utilized to form thefiber end face. Naturally, when costs are appropriate, the end face ofthe plastic fiber may be formed by polishing.

The end face of the ferrule 1 where the optical semiconductor device 3is placed is formed to make an angle with a surface vertical to thelight-guiding direction of the optical fiber 5. An inclination angle ofthis optical semiconductor device mounting face may be set so that theoptical fiber does not contact an active portion of the light emitter.An example will be shown below wherein the inclination angle of thismounting face is set.

In the ribbon fiber used in optical communications system in which alarge number of silica-based optical fibers are arranged, the respectivefibers are generally arranged in an array at a pitch of 250 μm, and, inmany cases, the light emitters are also designed to be arranged at apitch of 250 μm in conformity to the arrangement of the fibers, and theoptoelectronic conversion header 100 can be generally designed with easein this size.

On the other hand, the VCSEL has come into general use as a high-speedsurface light emitter 3. The VCSEL signifies a vertically resonantsurface emitting laser in general, but in general, it often exclusivelysignifies a vertically distributed Bragg reflector (DBR) surfaceemitting laser. In the VCSEL having an oscillation waveband of 850 nmwhich has become relatively generalized, Al_(x)Ga_(1-x)As is used for aDBR mirror, and in order to obtain a reflectivity of 99.9% or higherrequired as an oscillating condition, a pair of layers, for example,made of Al_(0.1)Ga_(0.9)As and Al_(0.9)Ga_(0.1)As having a thickness ofλ/4 needs to be repeatedly stacked to obtain a thickness of about 3.5μm. This is required for both a p-side and an n-side with an activelayer in between, resulting in a total thickness of 7 to 8 μm.

Furthermore, in the high-speed VCSEL, a selective oxidation structure isoften used as a structure to restrict an oscillation area where acurrent is confined. In the selective oxidation structure, a crystal(e.g., Al_(0.98)Ga_(0.02)As) having an extremely strong oxidizingproperty is thinly provided in the vicinity of the laser active layer,and is selectively oxidized from the outside by a vapor in a manner toleave a desired laser active area. By way of example, crystal layerssuch as a first DBR layer, an active layer, a selectively oxidized layerand a second DBR layer are sequentially stacked, and they are subjectedto mesa etching with a diameter of 30 μm and selectively oxidized fromtheir lateral side edge at a length of 10 μm, whereby the selectivelyoxidized VCSEL can be produced whose current injection aperture diameteris 10 μm. At this time, the mesa etching may be implemented at a depthto reach the selectively oxidized layer, and reaches a depth deeper thana DBR thickness of 3.5 μm, that is, a depth of about 4 μm.

Taking this selective oxidation structure into consideration, in a VCSELchip of 250 μm×250 μm, a distance from an edge to a center of the chipis 125 μm, and when a center of a emitting portion is set at a center ofthe device, a mesa having a height of 4 μm is formed up to 15 μm fromthe center. As a distance from the chip edge to a mesa edge is 110 μmand the height of the mesa edge is 4 μm, a straight line extending fromthe chip edge to the mesa edge has an inclination of about two degreeswith respect to a chip surface (4 μm/110 μm to tan 2°).

A dimensional relation of the structure is shown in FIG. 3. In FIG. 3,numeral 301 denotes a VCSEL substrate such as a GaAs substrate, numeral302 denotes a current injection aperture, that is, an active area of theVCSEL formed as a nonselective oxidation area, and numeral 303 denotes acircular mesa as the second DBR layer formed deeper than the selectivelyoxidized layer.

In FIG. 3, a line drawn from an upper left portion of the VCSELsubstrate 301 to an upper left portion of the circular mesa 303represents a virtual osculating plane, and a contact angle of this planeis about 2°, as described above. In the VCSEL, the device is less likelyto be broken even if the end face of the ferrule or the like contacts toa substrate surface such as a mesa-etched surface at a certain degree,unless the optical fiber 5 or the like contacts the circular mesa 303 inwhich the active area is formed. Thus, in FIG. 2, if a contact angle ofan object contacting the plane is 2° or more, the osculating planecontacts the substrate 301, so that the VCSEL active area 302 and/or thecircular mesa 303 is/are protected.

Therefore, in the VCSEL having a size of 250 μm×250 μm which correspondsto the array pitch of the general ribbon fiber, an area for the mesahaving a diameter of 30 μm which corresponds to the active portion isprevented from contacting the plane having an inclination of two degreesor more, thereby enabling the active portion to be protected. Thus, theend face of the ferrule 1 where the surface light emitter is placed isdesirably inclined two degrees or more with respect to the surfacevertical to the light-guiding direction of the optical fiber 5.

It is to be noted that this inclination angle is valid for a structurein which the end face of the optical fiber 5 sized more than the chiphaving a size of 250 μm faces the chip, but if the optical fiber havinga diameter smaller than 250 μm faces the chip, a greater inclinationangle is required. For example, the general silica-based optical fiberoften has a diameter of 125 μm, so that an inclination of about 5degrees is needed to align with the VCSEL a center of the optical fiberwhose diameter is 125 μm in order to protect the active portion of theVCSEL. That is, a distance from the fiber end to the mesa edge is 47.5μm, thereby satisfying 4 μm/47.5 μm to tan 5°.

The relation described above is shown in FIG. 4. In FIG. 4, numeral 301denotes the VCSEL substrate such as the GaAs substrate, numeral 302denotes the current injection aperture, that is, the active area of theVCSEL formed as the nonselective oxidation area, and numeral 303 denotesthe circular mesa, that is, the second DBR layer formed deeper than theselectively oxidized layer, dimensions of which are the same as those inthe example shown in FIG. 3. Further, numeral 5 denotes the opticalfiber which has a diameter of 125 μm as described above. Here, it isassumed that the end face of the optical fiber 5 is vertically cut, andits center (optical axis) is located in the center of the VCSEL activearea. In this state, if a condition is obtained under which the opticalfiber contacts the surface of the substrate 301 and a corner of thecircular mesa 303, the relation is shown in FIG. 4, and a contact anglebetween the end face of the optical fiber 5 and the VCSEL substrate isnearly 5°.

It is thus easily understood that, as shown in FIG. 4, if the end faceof the optical fiber 5 is inclined at 5° or more as described above, theend face of the optical fiber 5 contacts the substrate 301, so that theVCSEL active area 302 and the circular mesa 303 are protected. Inaddition, this relation is not satisfied if the optical fiber 5 and theVCSEL 3 are arranged without being brought into alignment with eachother to cause a misalignment of their centers, but as understood fromthe structure shown in FIG. 2, this results from a problem in alignmentwhen the VCSEL 3 is mounted to the ferrule 1. For accuracy in thisalignment, there is a method in which the optical fiber holding hole isaligned by use of image recognition thereof to allow an accuracy of ±5μm or lower. With further consideration of this alignment accuracy, ifthe inclination angle of the optical fiber, that is, the inclinationangle of the optical semiconductor device mounting face of the ferrule 1is 5.5°, the optical fiber does not contact the VCSEL active portion.

In this way, the optical semiconductor device mounting face of theferrule is inclined taking into account unevenness of a surface of theVCSEL, which can provide a configuration wherein the optical fiber doesnot contact the active portion of the light emitter. Naturally, thisembodiment is based on the assumption that a thickness of bump metals orthe like on which the optical semiconductor device is mounted issubstantially even within the surface and that there is substantially nochange in a relative angle between the optical fiber and the VCSEL evenif a temperature changes.

Furthermore, it is known that the oblique coupling of the optical fiber5 to the light emitter 3 also provides an effect of restricting anoccurrence of noise due to external feedback light. However, a distancefrom a light output surface of the light emitter (VCSEL) 3 to the lightinput end surface of the optical fiber 5 can be about 2 μm which isextremely short. Therefore, although the optical fiber and the VCSEL areinclined, reflected light rays from the optical fiber end face may becoupled to an optical resonance mode of the VCSEL 3 to produce theexternal optical feedback noise.

To alleviate this problem, the reflected light rays from a place veryclose to the end face of the optical fiber 5, particularly the reflectedlight rays whose optical path are located within a range of several μmmay be reduced to a low level, and a difference in refractive indicesmay be made as small as possible between the optical fiber (refractiveindex of about 1.46) and its surroundings (refractive index of 1 in acase of air). To narrow the difference in refractive indices, it iseffective to put a transparent material having a refractive index closeto that of the optical fiber 5 into a gap between the optical fiber 5and the light emitter (VCSEL) 3, which makes it possible to obtain aneffect similar to that when the optical fiber 5 is distanced from thelight emitter 3 in an equivalent manner due to a decrease inreflectivity caused by the narrowed refractive index difference. Whenthe transparent resin 6 is placed as shown in FIG. 2, the refractiveindex difference can be reduced. Thus, it is desirable that a refractiveindex of the transparent resin 6 be equal to or substantially equal tothe equivalent refractive index of the optical fiber.

Furthermore, use of the transparent resin 6 also provides an effect ofrestraining weak vibration of the optical fiber 5 due to external force.The optical fiber 5 contacts various objects outside the optoelectronicconversion header 100, and act as a vibration transmitting medium whichtransmits the external force from these objects to the inside. If theoptical fiber is subjected to external periodic vibration and thisvibration is located in the vicinity of a mechanical resonant vibrationfrequency, this might cause internal resonant vibration in which an endof the optical fiber 5 or the optical semiconductor device 3 contactingthe same weakly vibrates. The placing of the transparent resin 6described above is also effective in preventing and attenuating suchinternal vibration.

Moreover, the transparent resin 6 also has an effect of lessening adifference in thermal expansion characteristics between the opticalsemiconductor device 3 and the ferrule 1. The transparent resin 6 alsoprovides an advantage that stress or distortion due to the difference intheir thermal expansion coefficients does not concentrate on aconnection between the optical semiconductor device 3 and the ferrule 1,that is, a periphery of the mounting bump 4, and this stress ordistortion is dispersed over the optical semiconductor device 3 and theentire mounting surface opposite thereto. Thus, the use of thetransparent resin 6 is also advantageous in preventing degradation of aheat cycle and further increases its effect, so that it is alsoeffective to mix, into the transparent resin 6, a transparent fine grainfiller such as silica or crushed quartz having a mean particle diameterof several μm to several tens of μm. That is, a mixing rate of thetransparent fine grain filler is adjusted so that the average orequivalent thermal expansion characteristics of the resin conform tothose of the optical fiber and the optical semiconductor device or aredefined as their intermediate value, thereby allowing an increase in athermal stress (thermal strain) relieving effect.

FIG. 5 is a sectional view schematically showing the optoelectronicconversion header 100 at a receiving end according to the firstembodiment of the present invention, and shows a configuration in whichthe optical fiber 5 faces a photo detector 7 instead of the lightemitter shown in FIG. 1.

In FIG. 5, a numeral 1 denotes the ferrule which holds and positions theoptical waveguide such as the optical fiber or the light guide film. Theoptical fiber 5 will be described below as an example of the opticalwaveguide. Further, a numeral 2 denotes the electric wire or theextraction electrode patterned on the ferrule 1; a numeral 4 denotes theoptical semiconductor device mounting bump; a numeral 5 denotes theoptical fiber; a numeral 6 denotes the transparent resin as the opticalsemiconductor device under-fill material and the optical fiber adhesive;and a numeral 7 denotes a planar photo detector or a PIN photo diode(PIN-PD).

The ferrule 1 can be made of epoxy resin described above, and materialsother than epoxy resin can also be used. Further, the materials thathave already been described can be used for the bump 4 to mount theoptical semiconductor device 7 and for the optical fiber 5. The end faceof the optical fiber 5 is formed to be substantially vertical to thelight-guiding direction of the optical fiber 5 as in the structure shownin FIG. 3, and the method of forming this surface is as describedearlier.

The end face of the ferrule 1 mounting the optical semiconductor device7 is inclined at a small angle with respect to the surface vertical tothe light-guiding direction (optical axis) of the optical fiber 5. Ingeneral, the photo detector 7 often has a planar structure, that is, astructure whose surface is flat, and the end face of the optical fiberis not a completely vertical surface and is vertical in an irregularmanner, but the inclination angle of the optical fiber can be set to anoptional value if it is more than a range of irregularity in theverticality. However, the same ferrule as the ferrule holding the lightemitter shown in FIG. 3 can also be used for the ferrule 1 to beprovided with the photo detector 7, and if the inclination angle of themounting surface is set at 2° or more or at 5° or more when the opticalfiber 5 is proximate thereto, the ferrule 1 can be used in common forthe light emitter and the photo detector.

Furthermore, to restrain reflection at the receiving end, that is,reflection on the end face of the optical fiber 5 or on a surface of thephoto detector 7, it is effective to place the transparent materialhaving the refractive index close to that of the optical fiber 5 into agap between the optical fiber 5 and the photo detector (PIN-PD) 7. Thisrestrains reflection dependent on a refractive index difference at anoutput terminal of the optical fiber 5 between the optical fiber 5 andthe outside thereof, and it is desirable that the refractive index ofthe transparent resin 6 be equal to or substantially equal to theequivalent refractive index of the optical fiber 5. In addition, iflight rays reflected the receiving end is brought into the optical fiber5, this reflected light rays will reach the transmitting side to enterthe light emitter 3 at the transmitting side, thus producing noise atthe transmitting side. Therefore, the reflected light also needs to berestrained at the receiving end.

Furthermore, use of the transparent resin 6 also provides the effect ofrestraining the weak vibration of the optical fiber 5 due to theexternal force as described above, and is also effective in preventingand attenuating the above-mentioned internal vibration. Moreover, thetransparent resin 6 also has the effect of lessening the difference inthermal expansion characteristics between the optical semiconductordevice 7 and the ferrule 1, and is also advantageous in preventing thedegradation of the heat cycle as described above. In order to furtherenhance these effects, it is also advantageous to mix into thetransparent resin 6 the transparent fine grain filler such as silica orcrushed quartz having a mean particle diameter of several μm to severaltens of μm.

It is to be noted that when the optical semiconductor device is thesurface light emitter 3, the active area corresponds to the emittingportion which emits light by current injection and an area surroundingthe same. The active area generally signifies an area extending outwardfrom the emitting portion over 10 to 20 μm, or a mesa area which hasbeen processed so that the emitting portion is separated from theperiphery thereof. Further, in the photo detector, the active areacorresponds to a portion (light-receiving portion) of a depletion layerextending from a pn-junction or a metal semiconductor junction to applyan electric field to a light-absorption layer, and to an areasurrounding the same. The active area generally signifies an areaextending outward from the light-receiving portion over 10 to 20 μm, ora mesa area which has been processed so that the light-receiving portionis separated from the periphery thereof.

As described above, in the structure in which the end face of theoptical fiber is disposed proximately to the photo detector 7 andinclined with respect to the surface vertical to the optical axis, adistance between the optical fiber 5 and the photo detector 7 can bevery short, so that expansion of an optical beam after being emittedfrom the optical fiber can be minimized. That is, a light-receivingdiameter of a light-receiving area in the photo detector can be setslightly greater than a core diameter of the optical fiber to prevent adecrease in optical coupling efficiency, which is also effective inrestraining modal noise in multimode optical fiber transmission. Forexample, 10 μm can be added to the core diameter of the optical fiber(60 μmφ in a case of the optical fiber whose core is 50 μmφ) so that thelight-receiving diameter is slightly greater than the core diameter ofthe optical fiber.

The optoelectronic conversion header 100 at the light-transmitting endon which the light emitter 3 is mounted shown in FIG. 2 and theoptoelectronic conversion header 100 at the light-receiving end on whichthe photo detector 7 is mounted shown in FIG. 5 are effective indecreasing costs for the optical interface module and restraining theexternal optical feedback noise. In an optical fiber having a relativelyshort distance, for example, a length of 1 m or shorter, not only theoptical signal guided through the optical waveguide core 5A but also anon-guided light (cladding mode) propagating through the cladding 5B ofthe optical waveguide might be transmitted to the light emitter 3 at thetransmitting end. That is, an amount of light reaching the light emitter3 is not fixed due to the optical coupling efficiency between the lightemitter 3 and the optical waveguide core 5A, so that uncertain andeasily varying light might be transmitted to the light emitter 3.However, by using both the optoelectronic conversion header 100 at thelight-transmitting end on which the light emitter 3 is mounted shown inFIG. 2 and the optoelectronic conversion header 100 at thelight-receiving end on which the photo detector 7 is mounted shown inFIG. 4, the external optical feedback noise can be effectivelyrestrained. More specifically, there is a problem that the restraint ofthe reflected light at the light-transmitting end makes it easy forlight with a large angle which will be the cladding mode to beintroduced into the optical waveguide, and that without reflectionrestraint at the receiving end, the random reflected light due to thecladding mode will return to prevent stabilization of an operation ofthe VCSEL. However, as described above, by using both the optoelectronicconversion header 100 at the light-transmitting end on which the lightemitter 3 is mounted, shown in FIG. 2, and the optoelectronic conversionheader 100 at the light-receiving end on which the photo detector 7 ismounted, shown in FIG. 5, the stable operation can be performed even inthe optical interconnection system having a relatively short distance,for example, a wire length of 1 m or shorter.

As apparent from the above description, fields to which the presentinvention can be applied include a form wherein there is one opticalwaveguide 5, and one end of the optical waveguide 5 is provided in theoptoelectronic conversion header 100 at the light-transmitting end onwhich the light emitter is mounted, shown in FIG. 2, while the other endof the optical waveguide 5 is provided in the optoelectronic conversionheader 100 at the light-receiving end on which the photo detector ismounted, shown in FIG. 5. It is also apparent that the fields to whichthe present invention can be applied also include a form whereindifferent optical waveguides are optically coupled to an opticalconnector (not shown) by the optoelectronic conversion header 100 at thelight-transmitting end on which the light emitter is mounted and by theoptoelectronic conversion header 100 at the light-receiving end on whichthe receiving device is mounted.

It is to be noted that the above-mentioned inclination angle of theoptical fiber, that is, a maximum angle at which the surface of theferrule 1 to mount the optical semiconductor device is inclined withrespect to a vertical surface may be set as follows.

In the optoelectronic conversion header 100, a maximum light-receivingangle of the optical fiber 5 is defined as an upper limit of setting theoptical fiber inclination angle. That is, an angle more than thatexceeds a maximum waveguide mode angle of the optical fiber, so thatlight in a direction of a main axis (normal) of the VCSEL cannot becoupled. Thus, since the optical coupling efficiency unnecessarilydecreases beyond that angle, drawbacks will be greater. The maximumlight-receiving angle of the optical fiber 5 is about 12° (half anglevalue), in a case of the aforementioned silica-based multimode gradedindex (GI) fiber (having a core diameter of 50 μm, a cladding diameterof 125 μm and an NA of 0.21).

The half angle mentioned here is a half of a light-receiving full angleof the optical fiber (angle combining all positive components andnegative components of angular deviation from the main axis direction),and represents a value of maximum permissible angular deviation from themain axis direction. It is also possible to use themulti-compound-glass-based optical fiber or the plastic optical fiberfor the optical fiber 5, in which case it can have a still greaterlight-receiving angle (NA).

Next, in the optoelectronic conversion header 100 at the transmittingend, an optical coupling limitation between the optical fiber and theVCSEL includes an angle in which the maximum light-receiving angle ofthe optical fiber is combined with a light emission angle of the VCSEL.At an angle more than the above-mentioned optical fiber maximumlight-receiving angle, light having an angle in the main axis directionof the VCSEL cannot be optically coupled, but a light component at abottom part produced by an expanding angle of the light output from theVCSEL can be coupled, so that a physical limit will be an angle at whichthis coupled light substantially disappears. For example, the outputlight emission angle of the VCSEL is about 8° in signal mode oscillation(full width at half maximum: FWHM) and about 20° in higher-ordertransverse mode oscillation (full width at half maximum: FWHM).

Thus, a value in which each half angle is added to the maximumlight-receiving angle of the optical fiber will be the substantial limitof the optical coupling, and this value may be the inclination angle ofthe optical fiber in the embodiment of the present invention describedabove, that is, a maximum inclination angle of the surface of theferrule 1 on which the optical semiconductor device is mounted. In theoptical fiber described above, a maximum setting angle is 16° in thesignal mode oscillation VCSEL (sum of an optical fiber maximumlight-receiving angle of 12° and a half angle at half maximum of theVCSEL output light of 4°), or 22° in the higher-order transverse modeoscillation VCSEL (sum of an optical fiber maximum light-receiving angleof 12° and a half angle at half maximum of the VCSEL output light of10°), and there is little point in setting an angle more than theseangles.

Furthermore, in the optoelectronic conversion header 100 at thereceiving end shown in FIG. 6, when the optical fiber 5 has a diameterof 125 μm, a core diameter of 50 μm and a fiber NA of 0.21(light-receiving (emission) angle: θf=12°), a light irradiation areawidth W with respect to an inclination angle θt will be as follows: W=50μm when θt=0°, W=60 μm when θt=16°, W=70 μm when θt=25°, and W=80 μmwhen θt=32°. At 10 Gbps where the optical interconnection is moreadvantageous than the electric wire in a general printed wiring boardFR-4 (UL standard), if the light-receiving area diameter of thereceiving device exceeds 80 μm, there will be difficulty in operationdue to a limit of a CR product of parasitic capacitance thereof and animpedance of 50 Ω in a general transmission line. That is, in anoperation at 10 Gbps where the optical wire is effective, thelight-receiving area diameter of the receiving device needs to belimited to 80 μm or lower, and θt needs to be 32° at the maximum.

Thus, in the optoelectronic conversion header 100 of the presentembodiment, since the ferrule 1 holding the optical waveguide 5 such asthe optical fiber and the optical semiconductor device 3, 7 are mountedby use of the bumps 4 having nearly equal height, the inclination angleof the optical semiconductor device 3, 7 does not vary with atemperature change. Moreover, because its mounting surface is adapted tohave a normal deviated from an optical axis direction of the opticalwaveguide 5, a gap is automatically formed which corresponds to asectional width and deviation angle of the optical waveguide 5, therebymaking it possible to essentially prevent a problem that the opticalsemiconductor device active portion contacts and damages the opticalwaveguide 5. This can provide a setting where the active portion of theoptical semiconductor device is not damaged even if the opticalwaveguide 5 is brought in proximity to the optical semiconductor device3, 7 to the extent immediately before they contact or to the extent thatthey contact, so that the optical waveguide 5 can be brought intoproximity to the optical semiconductor device active portion up toseveral μm with satisfactory repeatability. Consequently, even if thelight-receiving diameter of the receiving device 7 is reduced to thecore diameter of the optical waveguide to achieve a higher speed, highlyefficient optical coupling can be implemented without using anyadditional article such as a lens which leads to a cost increase.

In this structure, since the optical semiconductor device 3, 7 isinclined with respect to the optical waveguide 5, the external opticalfeedback noise can naturally be restrained, and in particular, thetransparent resin 6 is put to restrain the reflection at an interface ofthe optical waveguide, so that even if the optical waveguide 5 isbrought into proximity to the optical semiconductor device 3, 7 atseveral μm, a distance effect surpasses an inclination effect torestrain the production of the external optical feedback noise. Further,the light input/output ends of the optical waveguide 5 (such as theoptical fiber and the light guide film) to exert the effects describedabove may be a vertical end face, and requires no costly obliqueprocessing such as oblique polishing. Moreover, extreme accuracy is notneeded for the light input/output ends of the optical waveguide 5 inorder to put the transparent resin 6 on the vertical end face, and aso-called cleaved end face is applicable. The present embodiment thushas an advantage that it is substantially free of trouble in terms ofprocessing costs. From such reasons, the high-speed LSI inter-chipwiring can be realized at low cost, which can be a significantcontribution to the upgrading of information and communicationequipment.

Second Embodiment

FIG. 7A is a plan view schematically showing a light emitter as anoptical semiconductor device mounted on an optoelectronic conversionheader 100 at a transmitting end according to a second embodiment of thepresent invention, and FIG. 7B is a sectional view along the VII-VIIline shown in FIG. 7A. FIG. 8A is a also plan view schematically showinga photo detector as an optical semiconductor device mounted on theoptoelectronic conversion header 100 at a receiving end according to thesecond embodiment of the present invention, and FIG. 8B is a sectionalview along the VIII-VIII line shown in FIG. 8A. A structure of theoptical semiconductor device itself may be of a mesa type such as thatof the VCSEL described above, but a type of device with low electrodecapacitance is shown here by way of example for the purpose ofhigh-speed operation.

In FIG. 7A and FIG. 7B, a numeral 301 denotes a semiconductor substrate,a numeral 302 denotes a laser oscillation area where a laser waveoscillates, a numeral 303 denotes a circular mesa, a numeral 304 denotesan insulating film, a numeral 305 denotes an active area electrode, and306 denotes a ground electrode. In FIG. 8A and FIG. 8B, a numeral 701denotes a semiconductor substrate, a numeral 702 denotes an inverseimpurity diffused area (light-receiving portion of pn-junction), anumeral 703 denotes a circular mesa, a numeral 704 denotes an insulatingfilm, a numeral 705 denotes an active area electrode, and a numeral 706denotes a ground electrode. In FIG. 7B and FIG. 8B, an optical fiber 5disposed opposite to the light emitter and the photo detector isindicated by a virtual line. An insulating film 304, 704 is an insulatorhaving a thickness that reduces a parasitic capacitance of the electrodefor high-speed operation of the device, and for example, a polyimidefilm having a thickness of 4 μm is used for this. This thickness isequivalent to the above-described depth of mesa etching of a VCSEL, andcorresponds to refill of a mesa etching area for selective oxidation.

Furthermore, if an array of the photo detectors (PIN-PD) is formed,holes are diffused due to a carrier density gradient when minoritycarriers and a non-diffused area are of an n type, and the mesa etchingis thus implemented to form a minority carrier diffusion preventioncavity for prevention of arrival at adjacent devices. In a PIN structureusing a direct transition type semiconductor material, it is often thecase that a depth of the impurity diffused area is about 1 μm and athickness of a light absorption layer is 2 to 3 μm, and the minoritycarrier diffusion prevention cavity may be formed to have a depth ofabout 4 μm. This minority carrier diffusion prevention cavity portion isrefilled with a mesa etching area in the same manner as the VCSEL,thereby providing a thick-film insulator to reduce the capacity of theelectrode.

Here, the active portion electrodes 305, 307 are the only parts neededto reduce electrode capacitance by use of the thick-film insulator, butall the bumps preferably have an equal structure and size in accordancewith the spirit of the present invention, so that the ground electrode306, 706 has the same configuration as that of the active portionelectrode. Thus, the entire device has a substantially flat surface, andthis makes a difference and provides a different function as comparedwith a case where a wiring pattern is connected (not shown) to theactive portion or connected to the substrate through the thick-filminsulator, but a mechanical configuration of a bump 4 as an electrodepad is not changed.

In this configuration, it is desirable that the electrodes 305 and 306or 705 and 706 be not formed except in an inclination direction of thesurface of the ferrule 1 on which the optical semiconductor device ismounted shown in FIG. 2, that is, the electrodes and the wires be notformed in a direction in which the optical semiconductor device isinclined when viewed from the optical semiconductor device activeportion. The reason for this will be described referring to FIGS. 9A and9B.

FIGS. 9A and 9B are diagrams schematically showing a configuration in anexample similar to that of the optoelectronic conversion header 100shown in FIG. 2, in which example a four-channel array of the lightemitters shown in FIGS. 7A and 7B is mounted as the opticalsemiconductor device. FIG. 9A is a top view from an opticalsemiconductor device mounting surface of the ferrule 1, and FIG. 9B is asectional view along the IX-IX line shown in FIG. 9A.

As understood from FIG. 9B, in this embodiment, the light emitter 3itself is obliquely disposed along a vertical direction of the drawing,and regarding the optical fiber 5 with a vertical end face, an edge ofthe optical fiber 5 is in contact with a vertical direction of the lightemitter 3, that is, a line along the IX-IX line on an outer peripheralside of the active area. It will be appreciated that such a manner ofcontact generates force by mechanical contact between the optical fiber5 and the light emitter 3, which might cause destruction or scratch ofthe on-chip electrical wiring metal of the light emitter. Thus, it ispreferable not to dispose an electrode at this contact portion. For thisreason, in the optical semiconductor device shown in FIGS. 9A and 9B,the electrodes 305, 306 are disposed in the diagonal direction of theoptical semiconductor device.

Third Embodiment

FIG. 10 is a sectional view schematically showing an optoelectronicconversion header 100 according to a third embodiment of the presentinvention. It is to be noted that the same numerals are assigned to thesame parts as those in FIG. 2, and these are not described in detail.

A structure shown in FIG. 10 is built in such a manner that a lightabsorbing resin 8 is additionally provided in the structure shown inFIG. 2. A light absorbing resin 8 includes, for example, carbon fineparticles, a pigment material, or epoxy resin, acrylic resin or siliconeresin into which germanium fine particles are mixed, and is formed intoa shape as shown in FIG. 10 by, for example, a resin mold. In thisconnection, it is preferable that the light absorbing resin 8 beprovided to have a thickness which makes it sufficiently opaque for awavelength used, for example, a thickness of 0.5 mm when a wavelength is850 nm and the resin contains the Ge particles at 20%, and the lightabsorbing resin 8 be formed to totally cover the outside of atransparent resin 6, but it may not cover some parts such as a partwhere a electrode is drawn. This light absorbing resin 8 functionseffectively in restraining external optical feedback noise as describedabove.

The transparent resin 6 placed to restrain the external optical feedbacknoise has an effect of restraining the reflection on the optical fiberend face, but cannot always achieve perfect correspondence of refractiveindices, so that there is often a slight amount of residual reflection.Light components produced by this residual reflection are oftenscattered and diffused around and lost when their medium is air, but inthis case, the transparent resin 6 has a refractive index higher thanthat of the ambient air and thus reflects a significant number of lightcomponents inward at an outer peripheral interface with the air. Thatis, there is a problem that the transparent resin 6 serves as a materialto confine light and prevents rapid scattering of the residual reflectedlight components, that is, the unnecessary light components. As aresult, the residual reflected light components are confined to become alight returning to the VCSEL, and it increases a level of backgroundnoise of the VCSEL. This increase in the noise causes an increase ofjitter when very fast optical transmission is performed, which is lessthan preferable. Moreover, in the optoelectronic conversion header 100at a light-receiving end, the transparent resin 6 closes a place wherethe light reflected on the surface of the photo detector should berapidly scattered and lost, and this light will travel back to theoptical fiber and reach a light emitter side.

To solve a problem of light confinement in the structure in which thetransparent resin 6 is used, the light absorbing resin 8 is provided ata part corresponding to the interface between the transparent resin 6and the air. A material whose refractive index is equal to that of thetransparent resin 6 can be used for the light absorbing resin 8. Inbrief, it is possible to use the transparent resin 6 into which thelight absorbing material is mixed. Even if the light absorbing resin 8and the transparent resin 6 do not have the same refractive index, resinmaterials generally easily achieve a refractive index of about 1.4 to1.6, so that a combination of materials is readily created which has avery small difference in refractive indices. Thus, in the structureshown in FIG. 10, almost no reflected light components are present at aboundary of the transparent resin 6 and those components are rapidlyabsorbed into the light absorbing resin 8.

In the light absorbing resin 8, light absorbers therein absorb residualreflected light, thereby restraining the light returning to the lightemitter 3. At this time, the light expands all over within thetransparent resin 6, so that even if the light absorbing resin 8 isremoved in some parts of the transparent resin 6, for example, in about10% of the surface thereof, the reflected light in those parts israpidly eliminated by other light absorbing resin contact portions, andthe light is not substantially stuffed inside. Therefore, it is of noimportance that some parts are not provided with the light absorbingresin 8 as described above. This holds true with a case where the lightabsorbing resin is not provided at portions corresponding to theelectrodes, for example, to create a recognition mark checking windowused during packaging.

It is to be noted that there is also an effective manner to form asecond transparent resin (not shown) similar to the transparent resin 6at a part corresponding to the light absorbing resin 8, instead ofproviding the above-mentioned light absorbing resin 8. According to thismethod, the boundary of the transparent resin 6 located in the vicinityof an exit of a gap between the optical semiconductor device and theferrule is extended to a farther position, so that the external feedbacklight reflected at the resin boundary does not easily travel back to thegap between the optical semiconductor device and the ferrule by spatialdiffusion. This is practically not a problem if the second transparentresin is provided to have a thickness more than a length from theoptical axis of the optical fiber to an end of the optical semiconductordevice.

The above-mentioned structure shown in FIG. 10 can be modified as shownin FIG. 11. In FIG. 11, while numerals 1 to 6 indicate the same parts orcomponents as those shown in FIG. 10, a numeral 8 denotes the lightabsorbing resin covering the entire optoelectronic conversion header100, a numeral 9 denotes an optical semiconductor device driving IC(such as a driver or receiver), a numeral 10 denotes a wiring substrate,a numeral 11 denotes a mounting substrate also serving as a heat sink,and a numeral 12 denotes a bond wire.

FIG. 11 is shows an embodiment in which the optoelectronic conversionheader 100 shown in FIG. 2 or 5 is applied to a LSI package with aninterface module shown in FIG. 1, and in this example, after theoptoelectronic conversion header 100, the optical semiconductor devicedriving IC and the like are mounted and electrically connected by thebond wire and the like, a protective molded resin is provided at a partcorresponding to the interface module. The light absorbing resin 8 andthe second transparent resin described above can be used as theprotective molded resin, and it is needless to mention that its effectincludes the restraint of the above-mentioned external optical feedbacknoise.

Fourth Embodiment

FIG. 12 is a sectional view schematically showing an optoelectronicconversion header 100 according to a fourth embodiment of the presentinvention. It is to be noted that the same numerals are assigned to thesame parts as those in FIG. 10, and these are not described in detail.

A structure shown in FIG. 12 is different from the structure shown inFIG. 10 in that an outer shape of a light absorbing resin 8 in FIG. 10is formed to extend from a ferrule 1 and that the optoelectronicconversion header 100 is seemingly formed as a rectangularparallelepiped chip.

In such a configuration, handling is easy because the opticalsemiconductor device is not exposed, and there is less limitation inpackaging. For example, even if the optoelectronic conversion header 100is exposed to a flux or a molten solder, it does not directly contactthe optical semiconductor device and is therefore not easily affected.Further, a light absorbing resin portion is prevented from overflow ofthe resin, so that even if an electrode extraction portion is brought inclose proximity to the mounting substrate, there is a little chance thatother components contact the mounting substrate before the electrodecontacts the mounting substrate. Thus, in this embodiment, a flip chiptype packaging method as shown in FIG. 13 can be applied.

In FIG. 13, electric wires (not shown) to connect the respective devicesare formed on a wiring substrate 10. In FIG. 13, a numeral 13 denotes anunderfill material on a flip chip mounting surface of the opticalsemiconductor device driving IC and the optoelectronic conversion header100, and 4A denotes a connection bump. Such a manner of mounting makesit possible to shorten a wire from the optical semiconductor devicedriving IC to the optoelectronic conversion header 100 and is effectivein improving high-speed operation characteristics.

Fifth Embodiment

FIGS. 14A, 14B and 14C are sectional views schematically showing aprocess of manufacturing an optoelectronic conversion header 100according to a fifth embodiment of the present invention. It is to benoted that the same numerals are assigned to the same parts as those inFIG. 2, and these are not described in detail.

In the process of manufacturing the optoelectronic conversion header 100according to this embodiment, a light emitter 3 is first mounted on aferrule 1 having an electrode 2 and an inclined optical semiconductordevice mounting surface. This process is implemented in such a mannerthat the active area pattern of the optical semiconductor device ismechanically aligned by image recognition with a guide hole for anoptical fiber and an electrode pattern of the ferrule. In this process,an accuracy of a mounting position is controlled, for example, within ±2μm. For example, thermal compression bonding of Au stud bumps is used toconnect an optical semiconductor device to the electrode 2.

Next, as shown in FIG. 14A, this ferrule is set to a jig 14 comprising,on its rear side, a stopper as a fixing wall which has the sameinclination angle as that of a surface of the ferrule 1 where theoptical semiconductor device is mounted. In this process, the ferrule 1and the jig 14 are not fixed, and a guide groove or the like is providedin the jig 14 so that the ferrule 1 can slide on the jig 14 only in adirection of the optical fiber guide hole. A material and configurationare considered for the guide groove of the jig 14 so that a frictionagainst the ferrule 1 is reduced. For example, fluorocarbon resin may bedisposed at a contact portion.

Next, as shown in FIG. 14B, an optical fiber 5 is inserted into theferrule 1. At this time, a transparent resin, that is, an adhesive 6 tofix the optical fiber may be first applied in a liquid state to decreasethe friction when the optical fiber is inserted. The optical fiber 5 isinserted by use of a device such as a micrometer with a depressionsensor which makes it possible to monitor pressure to insert the opticalfiber. Then, at a point where the insertion pressure has reached apredetermined pressure during the insertion of the optical fiber or at astarting point of the insertion pressure obtained by a differentialbetween the insertion pressure and an insertion distance, the insertionof the optical fiber 5 is stopped. The pressure at which the insertionof the optical fiber is stopped may be set at a pressure value which islower than a pressure at which an edge of the optical fiber is brokenand which does not cause cracks or the like of an optical semiconductordevice substrate.

Finally, as shown in FIG. 14C, the transparent resin 6 is solidified. Athermosetting resin or an ultraviolet curing resin is used for thetransparent resin 6, and when the optical fiber 5 reaches apredetermined insertion position, a curing treatment such as heating orultraviolet irradiation may be carried out.

The use of such a manufacturing method can preclude excessive externalforce from being applied to a connection of the optical semiconductordevice and the ferrule, that is, a bump electrode 4, and significantlyreduce faulty mounting of the optical semiconductor device, for example,dropping of the electrode. Parts which undergo the most external forceduring the insertion of the optical fiber include the optical fiber andthe optical semiconductor device substrate in the vicinity of a portioncontacting the optical fiber, whereas the bump electrode 4 is onlysubjected to force by the friction between the ferrule 1 and the jig 14.As described above, this can be reduced by devising a way to reduce thefriction in the jig 14 so that the friction between the ferrule 1 andthe jig 14 is reduced. For example, the jig 14 is vertically stood toset the ferrule 1 from above, whereby the friction between the ferrule 1and the jig 14 can be substantially brought to zero.

According to the optoelectronic conversion header 100 and the LSIpackage with the interface module of the present invention, thehigh-speed LSI inter-chip wiring can be realized at low cost, which canbe a significant contribution to the upgrading of the information andcommunication equipment.

There is a case where the optical fiber 5 of the LSI package describedabove is connected to another optical fiber or a case where the opticalfiber 5 is provided with an optical connector, and in order to connectsuch optical fibers or to manufacture such an optical connector, it ispreferable to cut/shape the end face of the optical fiber according toan optical fiber end face shaping method described below. Further, whenthis shaping method is implemented, a cover remover which will also bedescribed below is used to remove a cover of the optical fiber, and whenthe optical fibers shaped in this shaping method are connected, it ispreferable to use an optical fiber connector described below.

It is to be noted that in the optical fiber end face shaping methoddescribed below, for example, its end face processing or connectingoperation can be simplified, and this method can therefore be appliednot only to the end face processing for the optical fiber 5 of the LSIpackage but also to other technical fields such as opticalcommunications in which the optical fibers are used.

In general, the end face processing, that is, shaping/cutting of theoptical fiber is implemented to connect the optical fibers or to installthe optical fiber in the optical connector, and it is thus necessary tosmoothen a cut surface so that a great amount of optical loss is notcaused in the cut surface of the optical fiber.

In a known optical fiber end face processing method, after the cover ofthe optical fiber is removed, a small slash is caused to an opticalfiber by a cutting blade, and this portion is bent so that mirrorsurface breakage is caused to the optical fiber by use of brittlefracture of glass. There is also a method in which the optical fiber isbent together with the cover, and the cover is broken by putting thecutting blade thereon, and then a small slash is caused to the opticalfiber from the broken portion by the cutting blade to accomplish themirror surface breakage.

However, in the method in which the cover is removed to shape theoptical fiber end face, because the optical fibers are cut in a stateseparable from each other, fragments, that is, chips of the opticalfibers tend to be scattered. The scattered fragments are highly likelyto stick in a skin of, for example, a hand or foot, and in a worst case,they are carried through blood vessels by bloodstream to reach a heartor brain, which can place a life at risk.

Furthermore, in the method in which the optical fiber is shaped togetherwith the cover, it is possible to significantly reduce the scattering ofthe fragments of the optical fiber, but there is a problem that a yieldratio of cutting the optical fiber is extremely reduced due to athickness distribution of a cover material.

According to the optical fiber end face shaping method described below,a person who handles the optical fiber is not placed at risk, and yet itis possible to obtain characteristics comparable with those in a casewhere the optical fiber is only cut.

FIG. 15 is a perspective view schematically showing a ribbon opticalfiber to explain a method of shaping the end face of the optical fiberas a first referential example, wherein 110 denotes a optical fiberribbon, 111 denotes an optical fiber, and 112 denotes a cover resin ofthe optical fiber 111. In the method as the first referential example,after a tip of the cover resin 112 has previously removed, or in a statewhere the optical fibers 111 are displaced from the cover resin 112 sothat the optical fibers 111 are separated from each other to make itpossible to pull the optical fibers from the cover resin 112, theoptical fibers 111 are cut, for example, at a portion indicated by anarrow in FIG. 15. This causes a problem that fragments, that is, chipsof the optical fibers 111 tend to be scattered, and the scatteredfragments are highly likely to stick in the skin of, for example, thehand or foot.

The optical fibers generally used in the optical communications areoften made of a material such as quartz or multi-component glass, andthey are transparent and very thin, for example, with an outsidediameter of about 125 μm, and are thus difficult to visually recognize,which poses a problem that once they are scattered, it is substantiallydifficult to collect them. Moreover, they are very hard and thin, sothat the fragments thereof easily break into the skin, and if thosefragments enter the blood vessels, they can be carried through the bloodvessels by the bloodstream and reach the heart or brain, which mightplace a life at risk.

Such a risk is relatively known to optical fiber engineers, andattention is paid in handling the optical fiber fragments. However, theoptical fibers have come into use in fields other than the opticalcommunications, for example, in the optically wired device describedabove, and there is a higher risk of directly touching the fragments ofthe optical fibers without knowing the danger of the optical fiberfragments, for example, as if scraps of electric wires were handled.

Furthermore, when the optical fiber is actually cut, the optical fibers111 are held so that they are vertically sandwiched between two crampportions 141a, 141b, for example, as shown in FIGS. 16A and 16B, and acemented carbide blade 42 is moved between them in a manner to slightlyscrape the optical fiber as shown in FIG. 16B, thereby causing a smallslash thereto. Then, stress is applied so that a side on which thecemented carbide blade 42 has scraped will be convex (outside), therebycausing mirror surface breakage to the optical fibers 111. FIG. 16Ashows a section orthogonal to a longitudinal direction of the opticalfiber, and FIG. 16B shows a section parallel to the longitudinaldirection of the optical fiber. After the optical fiber has been cut,when the cramp portions are opened, for example, the cramp portion 141bis moved upward to finish end face shaping, the fragments or chips ofthe optical fibers are scattered around.

An optical fiber cutter has been developed which is provided with amechanism to collect the chips, but there still remains a problem of howto dispose of the fragments of the optical fibers. There is also aproblem of safety when the fiber has been unsuccessfully cut to producethe crushed fragments of the optical fibers. For example, it isnecessary to clean the cramp portions 141a, 141b of the optical fibercutter when the crushed fragments or the like of the optical fibers havebeen produced, but the chip collecting mechanism does not function todeal with the broken pieces or crushed fragments at that instance. As amatter of fact, there is a high risk of inadvertently shaking off thecrushed fragments in the cramp portions with bare hands, which is infact far from an essential resolution.

FIG. 17A is a sectional view showing a method of cutting the opticalfiber with the optical fiber cutter while the cover resin 112 is left.In the method shown in FIG. 17A, the cemented carbide blade 142 needs tocontact the optical fibers 111, for which purpose two ways can beconceived: one way to cause a slash to the optical fibers 111 whilecutting up the cover resin 112; and one way to implement cutting of thecover resin 112 separately from cutting of the optical fibers 111.However, both of the ways use a surface of the cover resin 112 as abasis, and it is not ensured that the cemented carbide blade 142 contactthe optical fibers 111 unless it is possible to guarantee an accuracy,for example, an error of 1 μm or less in a thickness of the cover resin112. More specifically, the cemented carbide blade 142 moves into theribbon optical fiber ribbon 110 as indicated by broken lines in FIG.17A, and contacts the optical fibers 111 at an erratic distance.

In general, a relatively elastic resin is used for the cover resin 112of the optical fiber, such as acrylic resin or silicone resin. Thus, aslight change in thickness is caused due to holding pressure of thecramp portions, and a thickness change is further caused by thermalexpansion due to an ambient temperature during operation. Further, afinished thickness, among others, changes depending on variations in aprocess during coating, on a cover resin structure and on whether thecover resin is single-layered or multi-layered, so that there is littlehope that a stable thickness is constantly provided. This might resultin a reduction in the yield ratio of cutting the optical fiber due tothe variations in thickness of the cover resin 112.

Next, a detailed description will be given to the optical fiber end faceshaping method, the cover remover and the optical fiber connector whichsolves the problems described above.

FIG. 18 is a perspective view showing a schematic configuration of theoptical fiber to explain the optical fiber end face shaping method.

In FIG. 18, a numeral 110 denotes the optical fiber ribbon, a numeral111 denotes the optical fiber, and a numeral 112 denotes the coverresin. The optical fiber 111 and the cover resin 112 are genericallycalled the optical fiber ribbon 110. Here, the optical fiber ribbon 110is shown as a so-called ribbon fiber in which a plurality of opticalfibers 111 is arrayed, but this optical fiber may have a single core.Moreover, the optical fiber 111 generally has a coaxial structure inwhich a cylindrical light guiding core is surrounded with a lightconfining clad, but it is shown without an internal structure in FIG. 18to FIG. 21.

In FIG. 18, the optical fiber 111 is, for example, a silica-basedoptical fiber having an outside diameter of about 125 μm, and the coverresin 112 is, for example, an acrylic UV (ultraviolet) cured resin, anda combined thickness of the optical fiber and the cover resin is, forexample, about 300 μm. The cover resin 112 may simply cover the opticalfibers as shown in FIG. 18, but may also have a double structure whichseparately covers the respective optical fibers and entirely covers thebound optical fibers.

First, the tip of the optical fiber ribbon 110 is folded together withthe cover resin 112 and roughly broken, thereby making the tip roughlyuniform. Here, the chips as the fragments of the roughly broken opticalfibers 110 are enclosed by the relatively soft cover resin 112, and theydo not stick in the skin unless they are force to do so. Further, forthe cover resin 112, the transparent resin is used which is easy tovisually recognize, and it is thus easy to visually recognize thefragments. Therefore, the fragments produced by the rough breakage maybe clipped by a general adhesive tape or sealed in a glass bottle or thelike and then discarded in the same manner as glass waste, which is notparticularly highly dangerous. Further, in the rough breaking operation,if the tips of the optical fiber ribbon 110 are not arranged in anextremely disorderly manner, a process of roughly making the tip uniformis not particularly required, and may normally be omitted.

Next, the cover resin 112 is partially removed as shown in FIG. 18. Forthis purpose, a plane blade (not shown) such as a razor made of carbonsteel for cutting tools is obliquely put toward the tip of the opticalfiber ribbon 110 in such a manner that an angle between the opticalfiber ribbon 110 and the plane blade is, for example, 30 to 45°, and theplane blade can only be slid to shave a side surface of the opticalfibers 111, thereby partially removing the cover resin 112. In order topartially remove the cover resin 112, the plane blade is made of amaterial harder than the cover resin 112 and softer than the opticalfiber 111, so that the surface of the optical fiber 111 willautomatically serves as a guide to remove the cover resin, whereby aproper amount of cover resin 112 is only removed to always leave areproducible shape.

Furthermore, the optical fiber ribbon 110 is damaged if the plane bladeis extremely strongly pressed on the optical fiber ribbon 110, so thatit is necessary to properly adjust pressing force. For example, in acase of a ribbon optical fiber having 12 cores (covered with an acrylicUV cured resin) which is a general silica-based optical fiber, the coverresin 112 can be removed with a force of about 2 to 3 N if the razormade of carbon steel for cutting tools is used, and the pressing forcemay be about 5 N at the maximum.

When the cover resin 112 is removed in the method described above, alayer of the cover resin 112 on one side of the optical fibers 111 isremoved as shown in FIG. 18, and if a section where the cover hasactually been removed is checked in detail, it has been found out froman experiment by the present inventors that the cover resin 112 isremoved as far as a portion between the optical fibers 111 which isslightly set back from a side of the optical fiber 111. This seems to bedue to the fact that when the cover resin 112 is shaved off by the planeblade, a portion where the cover resin has not been removed in thevicinity of a tip of the plane blade is mechanically pulled up, and thecover resin 112 is thus cut in a state extended outward beyond a sidetop portion of the optical fiber 111. This phenomenon is beneficial in anext process of shaping/cutting the optical fiber.

Next, the optical fiber 111 is shaped/cut, that is, cleaved orstress-broken. In this shaping/cutting, a cutting blade (not shown) madeof diamond or a cemented carbide alloy (e.g., WC using Co as a binder)is first rubbed against the surface of the optical fiber 111 along abroken line portion in FIG. 18, thereby forming a small slash (initialslash). Then, bending stress is applied in such a manner that a sidewhere the small slash is formed will be on the outside (convex portion).Instead of forming the small slash by the cutting blade, it is possibleto use a method in which pulse heating is performed by a thin lineheater to apply local stress or a method in which ultrasonic waves areapplied.

Here, in forming the small slash on the surface of the optical fiber111, it is difficult to determine a distance between the cutting bladeand the optical fiber surface due to a thickness distribution of thecover resin 112 in the example shown in FIGS. 17A and 17B describedabove. Contrarily, in this first shaping method, a most convex portionon a side to which the cutting blade is put is on the surface of theoptical fiber 111, the small slash or the like can be caused in a highlyreproducible manner. It is thus understood that, in causing the smallslash, this shaping method is characterized in that it can bring resultssubstantially equivalent to that in a method in which the optical fiber111 is totally exposed to cause the small slash.

Furthermore, when the cover resin 112 is removed in this shaping method,an outermost portion of the optical fiber 111 and the cover resin 112are arranged in the same plane where the small slash or the like iscaused, and it is thus possible that the cover resin 112 interferes withthe causing of the small slash by the cutting blade. However, asdescribed above, the outermost portion of the optical fiber 111 actuallyslightly protrudes from the cover resin 112, and the small slash can becaused without trouble.

As a result, the optical fiber 111 is shaped or cut in the broken linearea in FIG. 18, and the end face can be formed into a mirror surface,but the cut fragments of the optical fibers 111, that is, tip-sideportions from the broken line in FIG. 18 remain held by the cover resin112. That is, a state in FIG. 18 is seemingly maintained before andafter the shaping/cutting, and it looks as if slight bending is causedat a shaped/cut portion (broken line portion in FIG. 18) toward a sidewhere the cover resin 112 is not removed. Thus, the fragments are notscattered even if the optical fiber end face is cut, and this effect isprovided because an interface between the cover resin 112 and theoptical fiber 111 is not taken off and because the optical fiber 111 iscut in a state where the majority of the cover resin 112 (more than halfof the section) encloses the optical fiber 111. Therefore, it ispreferable to leave more than half of a cross-sectional area of thecover resin 112.

Subsequently, the optical fiber fragments (the tip side from the brokenline in FIG. 18) are separated in such a manner that, for example, theoptical fiber is folded toward the side where the cover resin 112 is notremoved to break the cover resin 112. The separated optical fiberfragments can be collected as the optical fiber 111 without beingscattered. It is to be noted that the fragments of the optical fiberscan also be processed without being separated, as described later.

FIGS. 19A to 19C are sectional views schematically showing a process ofremoving the optical fiber fragments described above using the coverremover.

In FIGS. 19A to 19C, a numeral 121 denotes a base member provided with aguide slot (guide hole) 122 for the optical fiber ribbon 110, 123denotes a discharge window for scraps, and 124 denotes a plane bladeobliquely attached, for example, at 30 to 45° so that its tip isdirected to an inner side of the guide slot 122. The guide slot 122enables the optical fiber ribbon 110 to be inserted straight therein,and is provided, at its inner portion, with a wall which defines aninsertion length of the optical fiber ribbon 110. Thus, the base member121, the guide slot 122, discharge window 123 and the plane blade 124constitute a cover remover 120.

Furthermore, the plane blade 124 is set so that a height of its tip froma bottom of the guide slot 122 is rather smaller than a distance whichis a sum of the outside diameter of the optical fiber 111 and a one-sidethickness of the cover resin 112. Then, when the optical fiber ribbon110 is inserted in a direction of an arrow in FIG. 19A, the tip of theplane blade is raised so that the height of the tip from the bottom ofthe guide slot 122 is raised to a height corresponding to a sum of theoutside diameter of the optical fiber 111 and a two-side thickness ofthe cover resin 112.

In order to realize, in a simplest manner, the above configuration toraise the tip of the plane blade 124, the plane blade 124 may be maderelatively long so that the tip height is changed by an elasticdeformation of the plane blade itself from its fixed portion to its tip.This is as if a thin razor were deformed by being pressed on a flatsurface, and this configuration can be built in a relatively simplemanner. Further, when the plane blade is configured as a thick blade sothat it is not easily deformed considering durability and cuttingproperties of the plane blade 124, a large space may be secured betweenthe tip of the plane blade 124 and the bottom of the guide slot 122, anda pressing portion may be provided to press the optical fiber ribbon 110to the plane blade 124 at a position opposite to the plane blade 124 byuse of a spring or the like.

Furthermore, as shown in FIG. 20A, the bottom of the guide slot 122remains flat, and the plane blade 124 is configured to verticallytranslate, so that the plane blade 124 may be pushed by a spring 31 in amanner to press the plane blade 124 onto the bottom of the guide slot122. Moreover, as shown in FIG. 20B, the bottom of the guide slot 122remains flat, and the tip of the plane blade 124 is configured to pivoton a shaft 32 for vertical movement, so that the plane blade 124 may bepushed by a spring 33 in a manner to press the plane blade 124 towardthe bottom of the guide slot 122. Still further, as shown in FIG. 20C,the plane blade 124 may be held so that it can slide in one direction byuse of a guide member 135.

Into the cover remover 120 configured as described above, the opticalfiber ribbon 110 is inserted as in FIG. 9A. At this point, the tip ofthe optical fiber ribbon 110 is adapted to reach the wall on the innerside of the guide slot 122, the cover resin 112 is removed at about thesame length every time. Then, as shown in FIG. 19B, the inserted opticalfiber ribbon 110 is pulled out in a reverse direction. In this way, asshown in FIG. 19C, the cover resin 112 is partially removed in a shapeas shown in FIG. 18.

Thus, if the cover remover used in this shaping method is employed, itsoperation only includes simply inserting and pulling out the opticalfiber ribbon 110, and in the first shaping method, an operation ofpartially removing the cover resin 112 can be performed in asignificantly simple and reproducible manner. In addition, the partialremoval of the cover resin 112 using the cover remover in this shapingmethod provides high reproducibility in its processed shape, and theoptical fiber cutter can be combined to effectively implement theshaping of the optical fiber.

FIGS. 21A and 21B show how another cover remover is used to partiallyremove the cover resin 112 so that the optical fiber cutter causes thesmall slash for shaping/cutting. The cutting blade 142 shown in FIGS.21A and 21B has its tip protruding as much as necessary to cause thesmall slash from an upper surface of the cramp portion 141a, and theside surface of the optical fiber 111 directly contacts the uppersurface of the cramp portion 141a, thereby making it possible to causethe small slash on about the same condition every time. This issubstantially equivalent to the method as shown in FIG. 15 in which theoptical fiber 111 is totally exposed to cause the small slash.

The processing up to the causing of the small slash is performed in theabove-described process, and bending stress is applied in such a mannerthat the side where the small slash is caused is on the outside toachieve shaping/cutting (stress breakage), which state is shown in FIG.22. In FIG. 22, 111a denotes a core of the optical fiber, and 111bdenotes a clad. For example, in a GI (Graded Index) type multimodeoptical fiber having a core diameter of 50 μm and a clad diameter of 125μm, the small slash is caused at a depth of, for example, 5 μm at whichthe small slash does not reach the core 111a. Further, a numeral 111cdenotes a fragment produced by cutting the optical fiber, and thisfragment remains at the tip of the optical fiber even after the opticalfiber end face has been shaped or cut as shown in FIG. 22. Subsequently,the fragment 111c can be torn off in a manner to fold it back, but it isalso possible to process the fragment in such a manner to leave it as itis, as shown below.

FIG. 23 is a sectional view schematically showing a connector to connectthe optical fibers shaped in the process above described.

In FIG. 23, a numeral 61 denotes a base member of the connector, 62denotes an optical connecting portion to insert the optical fiber 111,63 denotes an insertion portion to insert the optical fiber ribbon 110together with the cover resin 112, and 64 denotes a fragment containingportion to receive the fragments produced by the shaping/cutting theoptical fiber as shown in FIG. 22.

Holes having a diameter equal to that of the optical fiber ribbon 110are provided on the same straight line from both ends in a longitudinaldirection of the base member 161 to constitute the insertion portions63, and a hole having a diameter equal to that of the optical fiber 111is provided on the same straight line as that of the insertion portion163 to connect both the insertion portions 63 in order to constitute theoptical connecting portion 162. Moreover, a hole equal in size to theoptical fiber ribbon 110 is provided in a direction inclined withrespect to the insertion portion 163 to constitute the fragmentcontaining portion 164.

For the base member 161, a resin such as epoxy resin is used in which asilica filler is mixed at about 80% to conform a thermal expansioncoefficient thereof to that of the optical fiber, and it is formed intoa shape as shown in FIG. 23 by die shaping. The optical connectingportion 162 is made as a cylinder having a diameter of, for example, 126μm, so that displacement is reduced when the optical fibers 111 (whoseoutside diameter is 125 μm) bump into each other. The insertion portions163 are formed at an interval of 250 μm which is an array pitch for thegeneral ribbon optical fiber, for example, in a direction orthogonal toa surface of FIG. 23. At this point, an inclined surface produced withthe material of the base member 161 is formed between the opticalconnecting portions (cylindrical holes), and an angle and length of theinclined surface is adjusted so that the fragment 111c of the opticalfiber can pass when it is inserted from the insertion portion 163.

When the optical fiber processed as shown in FIG. 22 is inserted intothe optical fiber connector configured as above, the cover resin 112 ismoved under the guidance of the inclined surface between the opticalconnecting portions 162, and the fragment 111c of the optical fiber isdrawn by the cover resin 112 and thus enters the fragment containingportion 164. If the optical fiber is further inserted, the fragment 111cwhich has entered the fragment containing portion 164 will enter furtherinward, and the optical fiber is drawn thereby to move toward thefragment containing portion 164, but the optical fiber 111 tends tomove, due to its rigidity, in an extending direction of the insertionportion 163. As a result, the cover resin 112 is peeled off from theoptical fiber 111, whereas the optical fiber 111 moves toward theoptical connecting portion 162 and bumps into the optical fiber whichhas been similarly inserted from the other side, thus resulting in astate as in FIG. 24.

In this state, an optical adhesive is injected into the opticalconnecting portion 162 and the fragment containing portion 164 and thencured (e.g., heated), thus completing the connection of the opticalfibers. For the optical adhesive, for example, a transparent epoxy-basedadhesive, an acrylic-based adhesive or a silicone-based adhesive isused, and they may be cured on their curing conditions.

In the optical fibers thus connected, it is not necessary to process, aschips, the fragments 111c produced by the shaping/cutting as shown inFIG. 24, and safety can be significantly increased in an end faceshaping operation and connecting operation of the optical fibers. Endprocessing and connecting operation of the optical fiber according to athird shaping method include simple operations such as inserting andpulling the optical fiber into/from the cover remover, a cuttingoperation by the general optical fiber cutter, inserting the cut opticalfiber into the optical fiber connector, and injecting and curing theoptical adhesive, and the chips of the optical fibers are not basicallyproduced during these operations, and the fragments 111c are embeddedand fixed into the optical fiber connector by the optical adhesive (notshown), thereby making it possible to ensure essential safety.

It is to be noted that since the process of injecting the opticaladhesive can be performed before the insertion of the optical fiber tosmoothly insert the optical fiber into the optical fiber connector, theoptical adhesive may be injected first. Further, in the embodimentdescribed above, the optical fiber is inserted which has previously beenshaped/cut by the application of bending stress as in FIG. 22, but theoptical fiber which has been only slashed may be inserted, and theoptical fiber may be broken by the bending stress at a bending portionbetween the insertion portion 163 and the fragment containing portion164 in FIG. 23. In that case, the optical fiber cutting operation onlyincludes slashing, which is effective in eliminating the risk ofproducing the optical fiber chips due to unsuccessful breakage by theapplication of the bending stress.

FIG. 25 is a sectional view schematically showing another optical fiberconnector to connect the optical fibers shaped in the process describedabove.

The optical fiber connector shown in FIG. 25 has a basic structuresimilar to that shown in FIG. 23 and connects the optical fibers in thesame manner as the structure shown in FIG. 23, but it connects theoptical fibers 110 whose tips (fragments 111c) are bent toward the sidethe cover resin is not removed as shown in FIG. 23.

In FIG. 25, 71 denotes a base member of the connector, 72 denotes anoptical connecting portion to insert the optical fiber 111, and 73denotes an insertion portion to insert the optical fiber ribbon 110together with the cover resins 112.

For the base member 71, a resin such as epoxy resin is used in which thesilica filler is mixed at about 80% to conform a thermal expansioncoefficient thereof to that of the optical fiber, and it is formed intoa shape as shown in FIG. 26 by die shaping. The optical connectingportion 72 is made as a cylinder having a diameter of, for example, 126μm, so that displacement is reduced when the optical fibers 111 havingan outside diameter of 125 μm bump into each other. The insertionportion 173 has a space which accommodates a sum value of a doubleoutside diameter of the optical fiber 111 and a triple one-sidethickness of the cover resin 112. The optical connecting portions 172are formed at an interval of 250 μm which is an array pitch for thegeneral ribbon optical fiber, for example, in a direction orthogonal toa surface of FIG. 26.

When the optical fiber processed as shown in FIG. 26 is inserted intothe optical fiber connector configured as above, it moves in a mannerled by the shaped/cut surface of the optical fiber 111, and comes intothe insertion portion 173 while the optical fiber fragment 111c isfolded back. When the similarly processed optical fiber is inserted fromthe other side, the shaped/cut surfaces of the optical fibers 111 bumpinto each other at the optical connecting portion 172, thus resulting ina state as in FIG. 27. In this state, the optical adhesive is injectedand cured (e.g., heated), thereby completing the connection of theoptical fibers. For the optical adhesive, for example, a transparentepoxy-based adhesive, an acrylic-based adhesive or a silicone-basedadhesive is used, and they may be cured on their curing conditions. Inaddition, since the process of injecting the optical adhesive can beperformed before the insertion of the optical fiber to smoothly insertthe optical fiber into the optical fiber connector, the optical adhesivemay be injected first.

Owing to effects of the optical fibers thus connected, it is notnecessary to process, as chips, the fragments 111c produced by theshaping/cutting as shown in FIG. 27, and safety can be significantlyincreased in the end face shaping operation and connecting operation ofthe optical fibers. In this way, during the insertion of the opticalfiber, since it is inserted after folding the fragment 111c, theconnection of the optical fibers can be ensured without consideringpeeling characteristics of the cover in the optical fiber connector dueto characteristics of the cover resin 112 as in the third shapingmethod.

As described above, according to the above shaping method, thescattering of the fragments of the optical fibers is prevented so thatthe end face of the optical fiber can be shaped in a safe and simplemanner, and optical performance thus exerted can be equal to that whenthe end face shaping is implemented only with the optical fiber, therebyenabling optical connection which does not produce the fragments of theoptical fibers themselves. This allows the optical fiber to be appliednot only to specific fields such as the optical communications but alsoto universal fields, which can be a great contribution to prevalence ofthe optically wired device and the like leading to the upgrading of theinformation and communication equipment, for example.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventionconcept as defined by the appended claims and their equivalents.

1. An optoelectronic conversion header comprising: an optical waveguidewhich guides an optical signal and has an end face; a ferrule, having amounting surface, which holds the optical waveguide in a predeterminedposition so that the end face of the optical waveguide protrudes fromthe mounting surface; an electric wire provided on the mounting surfaceof the ferrule; and an optoelectronic converter having an opticalinput/output surface, which is electrically connected to the electricwire and is mounted on the mounting surface of the ferrule, the opticalinput/output surface being faced to the end face of the opticalwaveguide so as to transfer the optical signal along a transferdirection between the optical input/output surface and the end face ofthe optical waveguide, the end face being substantially vertical to thetransfer direction, and the optical input/output surface and themounting surface being deviated two degrees or more from a planevertical to the transfer direction.
 2. The optoelectronic conversionheader according to claim 1, wherein the ferrule has a side surfacecrossing the mounting surface, and the electric wire is formed to extendfrom the mounting surface to the side surface.
 3. The optoelectronicconversion header according to claim 1, wherein a transparent resin isprovided between the optical input/output surface and the end face ofthe optical waveguide.
 4. The optoelectronic conversion header accordingto claim 1, wherein the mounting surface is substantially parallel tothe optical input/output surface.
 5. An optoelectronic conversion headercomprising: an optical waveguide which guides an optical signal and hasan end face; a ferrule, having a mounting surface, which holds theoptical waveguide in a predetermined position; an electric wire providedon the mounting surface of the ferrule; and an optoelectronic converterhaving an optical input/output surface, which is electrically connectedto the electric wire and is mounted on the mounting surface of theferrule, the optical input/output surface being faced to the end face ofthe optical waveguide so as to transfer the optical signal along atransfer direction between the optical input/output surface and the endface of the optical waveguide, the end face being substantially verticalto the transfer direction, and the optical input/output surface and themounting surface being deviated two degrees or more from a planevertical to the transfer direction.
 6. The optoelectronic conversionheader according to claim 5, wherein the ferrule has a side surfacecrossing the mounting surface, and the electric wire is formed to extendfrom the mounting surface to the side surface.
 7. The optoelectronicconversion header according to claim 5, wherein a transparent resin isprovided between the optical input/output surface and the end face ofthe optical waveguide.
 8. The optoelectronic conversion header accordingto claim 5, wherein the mounting surface is substantially parallel tothe optical input/output surface.
 9. The optoelectronic conversionheader according to claim 8, wherein the optoelectronic converter iselectrically connected to the electric wire via a plurality of metalbumps.
 10. The optoelectronic conversion header according to claim 9,wherein the plurality of metal bumps has substantially same thickness.11. The optoelectronic conversion header according to claim 10, whereinthe optoelectronic converter includes an electrode connected to anactive region of the optoelectronic converter via the metal bump, thedistance between the optoelectronic converter and the optical waveguidevaries from a minimum distance, and the electrode is provided in aregion other than a region where a distance between the optoelectronicconverter and the optical waveguide is the minimum.
 12. Theoptoelectronic conversion header according to claim 9, wherein theoptoelectronic converter includes an electrode connected to an activeregion of the optoelectronic converter via the metal bump, the distancebetween the optoelectronic converter and the optical waveguide variesfrom a minimum distance, and the electrode is provided in a region otherthan a region where a distance between the optoelectronic converter andthe optical waveguide is the minimum.
 13. The optoelectronic conversionheader according to claim 8, wherein the optoelectronic converterincludes an electrode connected to an active region of theoptoelectronic converter, the distance between the optoelectronicconverter and the optical waveguide varies from a minimum distance, andthe electrode is provided in a region other than a region where adistance between the optoelectronic converter and the optical waveguideis the minimum.
 14. The optoelectronic conversion header according toclaim 5, wherein the optoelectronic converter is electrically connectedto the electric wire via a plurality of metal bumps.
 15. Theoptoelectronic conversion header according to claim 14, wherein theplurality of metal bumps has substantially same thickness.
 16. Theoptoelectronic conversion header according to claim 15, wherein theoptoelectronic converter includes an electrode connected to an activeregion of the optoelectronic converter via the metal bump, the distancebetween the optoelectronic converter and the optical waveguide variesfrom a minimum distance, and the electrode is provided in a region otherthan a region where a distance between the optoelectronic converter andthe optical waveguide is the minimum.
 17. The optoelectronic conversionheader according to claim 14, wherein the optoelectronic converterincludes an electrode connected to an active region of theoptoelectronic converter via the metal bump, the distance between theoptoelectronic converter and the optical waveguide varies from a minimumdistance, and the electrode is provided in a region other than a regionwhere a distance between the optoelectronic converter and the opticalwaveguide is the minimum.
 18. The optoelectronic conversion headeraccording to claim 5, wherein the optoelectronic converter includes anelectrode connected to an active region of the optoelectronic converter,the distance between the optoelectronic converter and the opticalwaveguide varies from a minimum distance, and the electrode is providedin a region other than a region where a distance between theoptoelectronic converter and the optical waveguide is the minimum.